package main

import (
	"fmt"
	"strings"
)

func main() {
	input := "Hello, world! This is a demo string with spaces, dots, and hyphens."
	replacer := strings.NewReplacer(" ", "_", ".", "_", "-", "_")
	output := replacer.Replace(input)
	fmt.Println(output)

	a := "hello"
	b := "world"

	fmt.Println(strings.Join([]string{a, b}, "_"))
}
